Mold cooling system and method for polymerizing resins



June 1 R. SONNEBORN ETAL 3,387,325

.MOLD COOLING SYSTEM AND METHOD FOR POLYMERIZING RESINS Qriginal FiledMay 27, 1964 4 Sheets-Sheet 1 THE ENVIRONMENT 418% Y 451 THE PROBLEMRALPH H; 50NN50kN 8:

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MOLD COOLING SYSTEM AND METHOD FOR POLYMERIZING RESINS Original FiledMay 27, 1964 4 Sheets-Sheet 5 13 4 INVENTORS PAL/7H H Sam/50,? & Regn/4W0 ALVA/e52 DE E4500 Arrow/5Y5 June 11, 1968 R. H. SONNEBORN ETAL3,387,325

MOLD COOLING SYSTEM AND METHOD FOR POLYMERIZING RESINS Original FiledMay 27,1964

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4 T TORA/E v5 United States Patent 3,387,325 MOLD COOLING SYSTEM ANDMETHOD FOR POLYMERIZING RESINS Ralph H. Sonneborn, Newark, Ohio, andFernando Alvarez De Toledo, Crainhem, Belgium, assignors to Owens-Corning Fiberglas Corporation, Toledo, Ohio, a corporation of DelawareOriginal application May 27, 1964, Ser. No. 370,535, now Patent No.3,337,674. Divided and this application Nov. 14, 1966, Ser. No. 606,435

8 Claims. (Cl. 18-6) ABSTRACT OF THE DISCLOSURE Mold cooling system andapparatus wherein a mold plate is placed adjacent to a body ofheat-exchange liquid and means is provided for developing a multiplicityof droplets from the heat-exchange liquid and propelling the dropletsinto direct contact with the mold plate.

This is a division of copending application Serial No. 370,535 filed May27, 1964 and now Patent No. 3,337,674.

This invention relates to the polymerization of resin systems havingexotherms of reaction; still more particularly the invention relates toa mold cooling system for controlling the polymerization of resinshaving sharp and high exotherms of reaction; and also to a method ofpolymerizing such resins.

THE PROBLEM In the production of molded articles from resin systemsdisplaying high and sharp exotherms of reaction, there is a substantialproblem of controlling the polymerization against run-away. Unless thisis done, the monomer component of the resin may boil, producingbubble-like defects in the article which will cause the part to berejected. This is a particularly acute problem in acrylic resin systemsbecause they are characterized by the development of such high exothermsof reaction that the monomer component will be boiled quite readilyunless the exotherm is carefully controlled.

In one prior system, the polymerizing layup was run over a corrugatedmold, or other, to develop the shape, and retained on such mold for'asufiicient time to allow the resin to polymerize to a hard solid state.

Two methods of cooling the polymerizing resin in order to preventmonomer boil have been used in that prior system, as follows:

In the first method, a platen through which water as a heat-transfermedium was circulated, had a replaceable mold plate on top of it.However, because of the corrugations of the mold, air pockets wereproduced between the mold plate and the platen top so that accuratecontrol was often difficult because of the retarding effect against fastheat-exchange caused by theair pockets. This system had the advantage ofease of mold replacement, but the consequent disadvantage of the airpockets that introduced a difficult control factor, outweighed theadvantage.

In the second method, the top of the lower heat-exchange tank wasactually formed as the mold surface. This provided better heat transferbut presented the difficulty that every time a shape was to be changed,the entire lower mold tank had to be replaced. This proved to beprohibitively expensive because of the many shapes involved. Also, timewas consumed for disconnecting and setting a different tank into placeevery time a run of another cross-sectional configuration of panel wasto be made.

Accordingly, the present invention is an improvement 3,387,325 PatentedJune 11, 1968 over the prior methods, and also is extensible in scopesubstantially therebeyond for controlling resin polymerization invarious kinds of layup and formation systems. Therefore, a substantialadvance to the art is provided by the present invention wherein moldplates of any shape are uniformly cooled by intimate contact with aheat-transfer medium, and while such mold plates are either:

stationary and opposed for continuous production through them;

individual and continuously moved;

individual and intermittently moved;

or individual and held stationary.

It is therefore an important object of the present invention to providea novel mold cooling system for polymerizing resins having hard tocontrol exotherms o polymerization.

A further object is to provide a fool-proof system to cooling a moldcarrying a polymerizing resin, that utilizes droplets of water, asdistinguished from a fine mist or spray, to intimately wet the oppositeside of the mold surface and thereby provide a perfect heat transferwith the resin exotherm.

A further object is to provide a novel apparatus for cooling moldscarrying polymerizing resins, that generate exothermic heat, by applyingwater as a heat-sink or heat-transfer medium to the opposite side of themold without the use of sprays, that would be troubled by clogging bydeposition of the minerals contained in the water.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

FIGURE 1 is a fragmentary isometric view of a continuous panel linewherein the exotherm of polymerization of a resin is controlled while ashape is being stabilized, and illustrating an environment for thepresent invention;

FIGURE 2 is a sectional view taken along the line 22 of FIGURE 1,specifically illustrating the problem solved by the present invention;

FIGURE 3 is a sectional view showing schematically the manner in whichthe problem has been solved in accordance with the present invention;

FIGURE 4 is a sectional view taken along line 4-4 of FIGURE 3;

FIGURE 5 is a fragmentary top plan view of the mechanism of theinvention;

FIGURE 6 is a fragmentary sectional view taken along line 6-6 of FIGURE5;

FIGURE 7 is a sectional view taken along line 77 of FIGURE 5;

FIGURE 8 is a top plan view of the motor, and its mounting, for drivingthe splasher paddles utilized in FIGURE 5;

FIGURE 9 is an elevation view taken along the line 9-9 of FIGURE 8;

FIGURE 10 is an enlarged, side elevation view of a center bearing usedin FIGURE 5;

FIGURE 11 is an enlarged, fragmentary transverse sectional view similarto FIGURE 7, showing the spill trough and the splasher paddleconstruction in greater detail;

FIGURE 12 is a transverse sectional view of a splash paddle, the size ofFIGURE 11;

FIGURE 13 is a top plan view, schematic in nature, and illustrating thefluid flow pattern used in the invention;

FIGURE 14 is a fragmentary perspective view taken along line 14-14 ofFIGURE 13, showing the water 3 level control mechanism at the outlet endof FIGURE 13;

FIGURE 15 is a schematic side elevational view of a continuousproduction line using individual molds, as distinguished from thecontinuous, opposed mold system of FIGURES 1-15;

FIGURE 16 is a schematic side elevational view illustrating the extendedscope of invention as applied to an incremental system; where individualmolds are advanced by steps through the process; and

FIGURE 17 is a schematic side elevational view of apparatus and processwherein a one station mold is utilized.

It is to be understood that the present invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the drawings, since the invention is capable of otherembodiments and of being practiced or carried out in various ways. Also,it is to be understood that the phraseology or terminology employedherein is for the purpose of description and not of limitation.

Perspective view Briefly the present invention relates to a novelmechanism, and system, for controlling the exotherm of polymerization ofsynthetic resins, wherein water is used as a typical heat-exchangemedium. In this invention, the heatexchange medium is distributeddirectly upon one surface or side of a mold carrying a polymerizingresin mass, in droplet form, as distinguished from a fog or mist,thereby providing a fast and intimate heat transfer, and perfect controlof the polymerizing resin. Along with the foregoing, the presentinvention provides rapid and economical mold change. The initial part ofthe disclosure will be directed to a continuous panel line Where patiopanels and the like are produced. The last part of the disclosure willillustrate the invention as applied to individual molds for resin layupsthat are:

(a) Continuously moved in a production process;

(b) Intermittently moved in a stepwise manner in a production process;or

(c) Held stationary while layup, resin gel, and resin polymerization areall effected at one position.

The environment of the present invention FIGURE 1 illustrates afragmentary portion of a continuous panel line wherein an acrylic resinsystem is combined with reinforcing fibers and retained betweenimpervious membranes such as cellophane, while the resin is polymerized.A shape is developed, of suitable crosssectional configuration, andmaintained in the molded form until the resin has passed the peakexotherm temperature.

As shown in FIGURE 1, a layup 30 is being propelled in the arrowdirection 32 through a molding and curing mechanism. A lower tank 34,suitably containing heated water as an energy transfer medium, serves asa first support over which the layup 30 is passed. This is thepreforming phase. The purpose of this tank 34 is to warm the resin ofthe layup to a level to initiate polymerization and carry thepolymerization to the gel stage. Thus, in the subsequent shapedevelopment section 36 the resin will remain immobile and not flow. Thisassumes a uniform thickness throughout the corrugated or other section,and extending entirely across the panel.

The shape development section 36 includes a lower tank 38 that has amold plate 40, FIGURE 2, suitably secured to the upper surface thereof.An appropriate entrance mouth is provided at 42 to facilitate thedevelopment of a corrugated shape from the entering flat shape 30.

An upper tank 44 floats on the layup as it passes over the bottom moldplate 40. This is tethered by means of cables 51, connected to a bracketarm 52. The bottom 46 of upper tank 44 is of a shaped configuration,complementing that of the bottom mold plate 40. As shown in FIG- URE 2,the layup 30 is carried between the mold surfaces 4 40 and 46 during thetime that the shape is solidified by controlled polymerization of theresin.

The shape developing and retaining force is indicated by the arrows 48,FIGURE 2. This is provided by the weight of water in the top tank 44.

The body of water 50, retained in the upper tank 44, and the body ofwater 62, in the lower tank 38, not only act as a polymerizationinitiator, but also as a heat sink. Thus, since it is heated, it willcause the resin to polymerize. Further, when the exotherm of the resinoccurs, heat is absorbed by the water and the polymerization isprotected against run-away, once it reaches a high rate of activity.

It is to be understood that the water is continuously circulated throughthe tanks and back to a heat-exchanger by means not shown, to eitherheat or cool it as necessary. Thus, the water is maintained at anappropriate temperature level for the processing.

After the resin is polymerized to a hard solid state, it leaves theshape-development section 36 and passes to a post-curing oven 53.Between the outlet end of shapedevelopment section 36 and the entranceinto the oven 53, upper and lower sets of drive rolls 54 frictionallyengage the laminate and propel it forwardly, with power provided by adrive motor 56.

The problem This is illustrated in FIGURE 2 of the drawings, wherein airpockets 58 exist between the apexes of the corrugations of lower moldplate 40 and the flat tank top 60. Even though the lower tank 38 ismaintained full of water, clear to the top 60, the air pockets 58 hindereffective heat transfer between the polymerizing layup 30, and the water62 in lower tank 38. Further, heat transfer is required through moldplate 40 and tank top 60 both, before it reaches the water 62, or viceversa, depending upon whether polymerization is being initiated or theexotherm controlled.

Although the system illustrating the problem has met with an appreciabledegree of success, and although many satisfactory panels have been madetherefrom, it lacks the quickness of control required when processingacrylic resins. These have such a high and sharp exotherm ofpolymerization, that very fast response is required for high qualityproduction. For example, when an acrylic system gets started'runningway, it can reach 330 F. in a period of time measured almost in seconds.tI will be evident that unless exact and intimate heat exchange isprovided, monomer boil will be the mandatory result, and the productwill be ruined.

The present invention has overcome this problem and smoothed outproduction in such a remarkable manner that it is submitted that theinvention is not only applicable in the previous environment, but alsoextensible to other types of resin polymerizing and handling systems aswill be discussed hereinafter.

The invention schematically illustrated FIGURES 3 and 4 illustrate themanner in which an open top tank 64 is utilized to retain a body ofwater 66 held at a controlled temperature level. A plurality of splasherpanels 68 are positioned transversely of the tank 64, as illustrated inFIGURES 3 and 5. These are rotated, and dipped into the body of water 66to pick up the water and throw it as droplets 67 up against the bottomside of the lower mold plate 40. It is to be noted that the droplets 67are distinguishable from a mist or fog. They thus wet the mold plateadequately and provide perfect heat transfer through the mold plate 40to the polymerizing resin 30.

In accordance with the present invention, the following advantages areprovided:

The lower mold plate 40 is readily replaceable as shown in FIGURE 2; and

Perfect heat transfer for exact control of acrylic resin systems,typifying those with high exotherms of polymerization, is provided.

The invention in detail FIGURE 5 provides a general overall view of theinvention from a position analogous to that of the bottom surface of thelower mold plate 40, looking down into the mechanism utilized to developthe water droplets. The main, central tank 70 comprises a bottom 72 andside walls 74. The top is open. Around the outside of the tank is aspill or overflow trough 76 of U-shaped section as shown in FIGURE 7.

As shown in FIGURE 5, the inside wall 78 of overflow trough '76 issuitably fastened by bolting as at 80.

It is to be understood that sidewalls 74, 78 and 82 are of suflicientlythick material to provide support for outboard bearings 84 for thesplasher units 86.

Extending transversely across the tank 70 are a plurality of spacedsheet metal rib members 88. These are formed of generally U-shapedconfiguration, as shown in FIG- URE 6, with overturned edge flanges 90for longitudinal stiffness. At their ends, the rib members 88 aresuitably welded to the inside surfaces of the side walls 74, and alongthe lower edge to the bottom 72, and thus are held in position. It willbe noted that these rib members 88 extend transversely of thelongitudinal axis of the tank 70 and are spaced axially and parallel toone another along the length of the tank.

The central tank 70 is of substantial width. If the splasher units 86spanned the tank 70, they would be unduly long and there would be whipduring their rotation. Accordingly, longitudinally oriented spacer walls92 are provided down the center of the unit. These, as shown in FIGURE5, are also of generally U-shaped section with the over-turned flanges94 providing stiffness. These units are extended between the end walls75 and all of the transverse rib members 88, and fastened with bolts 96.As shown in FIGURE 6, these units are fitted beneath the top overturnededges 90 of the sheet metal rib members 88 for simplified fabrication.However, they are of a width such that they do not extend clear to thebottom tank wall 72 in order that the heat exchange medium can flowfreely over the bottom '72.

The purpose of the longitudinally disposed spacer walls 92 is to supportcenter bearings 98 forming part of the splasher units 86. As shown inFIGURE 10, this hearing is made of Micarta and thus selected foroperation under conditions where it is exposed to the water spray and isactually lubricated by the spray being conducted'to the bearingsurfaces. Micarta is a trademark for heavy-duty, ther-mo-setting,plastic materials made from fabric or paper impregnated withphenol-formaldehyde resins and compressed under heat into a permanentlysolid substance with high structural and dielectric properties. Theparts so made are resistant to corrosion under conditions of highhumidity such as contemplated here, and with water as a lubricant, forma fine-bearing material for drive shafts as typified by shaft 108.

This construction is shown in FIGURE 10, and comprises upper and lowerbearing halves 108 and 102 that The configuration 0f the splasherassemblies By referring to FIGURE 12, the sectional configuration of thesplasher assemblies can be described. As there shown, three separateblade units 114 are fabricated together to make a single assembly. Eachblade unit 114 is of stainless steel sheet stock for strength andcorrosion resistance, although the broad scope of invention wouldinclude other equivalent materials. In the raw sheet form this is anelongated rectangular strip.

Along one edge there is an upturned flange 116. This is placed incontact with the opposite flat edge of the next blade unit 114. Thethree blades are put together in the same fashion.

Spot welds 118 along the length of the flanges 116 secure the componentstogether in assembled array.

The triangular enclosure produced by the foregoing orientation of theblades is of such a size that the central portions of the blades snuglyengage shaft 108. This provides rigid support against the units floppingor whipping relative to the shaft during their rotation.

Referring now to FIGURE 11, note the end washer 120. One of these issecured to each end of a blade set. The washer 120 has a center hole, tobe fitted upon shaft 108. Set screws 122 pass radially through thewashers and are tightened down to engage the outside of shaft 108. Thislocks the blade assembly 114 to the shaft for rotation.

A word at this time is important regarding the configuration of thesplasher units. This particular design is the result of extendedresearch and has been found to provide much improved droplet developmentover other configurations. For example, squirrel cage fan configurationswere tried with two, three and more blades but with lesser efliciency inthe effect. Here, the counter-clockwise rotation of the units in thedirection 124, FIGURE 12, provides a dipping action and then a throwingaction analogous to the human hand whereby very small droplets areproduced, which are clearly distinguishable from a fog, mist, or finespray. This provides the extremely good heat exchange and polymerizationcontrol mentioned herein-before.

The fact that the central portions of the blades 114 cmbrace the shaftall along the length in a very close manner provides an extremely rigid,rod-like unit. This is more rigid than a squirrel cage unit where longflexible blades are attached only at the ends to support plates. Ifintermediate webs are used in a squirrel cage structure, of course thecosts of fabrication are substantially increased.

Uniform droplet pattern produced by the splasher assemblies Referring toFIGURE 5, note that the longitudinally disposed spacer walls 92 arestaggered on each side of the axial center line of tank 70. Theoverturned flanges 94 make this possible with the flanges beingpositioned opposite one another on each side of rib members 88. With thebearing members 98 positioned on the outside of the bight portion ofeach spacer wall 92, a zigzag pattern of these units is produced.

Between a bearing 98 and its adjacent side wall 74 there is used aso-called short blade assembly between the other side of the spacer wall92 and the other side 74 of tank 70, there is a greater distance to bespanned. Thus a so-called long splasher unit 87 is utilized. This meansthat down the length of the tank, the units 85 are staggered, as alsoare units 87. The important point is that the ends of the units 87overlap to produce a continuous spray pattern without gaps at thecenter. The effect in actual operation is substantially equivalent tothe splasher units 86 extending from side wall to side wall 74, 74 oftank '70.

Actually the droplct pattern produced is unexpectedly uniform as theresult of the configuration of parts utilized. This is an importantfeature along with the fact that the splasher units 86 have centersupport for added rigidity and resistance against whip.

End support of the splasher-s Refer to FIGURES 7 and 11 for thefollowing discussion:

On the outside of walls 82 of the overflow trough 76 are securedbearings 84. Those actually used were scaled ball bearing pillow blockunits but still required protection from direct exposure to the hotwater contained in tank 70. These ball bearings of course, aredistinguished from the Micarta bearings 98 which are specificallydesigned to withstand exposure to water. However, if Micarta bearingswere used all the way through, frictional resistance would be undulyhigh.

By placing the bearings 84 on the outside of the outer walls 82 of theoverflow trough 76, they are thus isolated from the water spray. Thetrough 76 serves to catch any spill and drain it away, to protect thebearings 84. The lubrication that is normally packed into these bearings84, preferably water pump grease, is effective to resist atmosphericmoisture in the normal manner.

Further, as shown in FIGURE 11, shaft 108 extends through walls 74 and78 without engagement therewith, by the fact that the hole 126 is alittle larger than the shaft. An advantage at this point is that thebottom porions of the holes 125 facilitate overflow into trough 76, whensuch conditions arise, and such overflow is carried away by drain holes128, connected to conduits 130. This arrangement also diminishes theneed for tight seals to prevent leakage and which usually requireconstant maintenance.

At this point referring to FIGURE 11, a further utility feature ofoverflow trough 76 becomes apparent. The bottom mold plate 40 issuitably bolted in position on a bracket arm 133, with the outer edgeextending over trough 76. Drip 132 from the underneath side is thus freeto fall into trough 76 and be carried away. This provides goodhousekeeping around the machine and obviates the necessity for floordrains that would otherwise be required.

Schematic flow through the system This is shown in FIGURE 13 where aninlet conduit 134 is provided at one end of tank 70, and an outletconduit 136 is provided at the other end of the tank.

As regards integration of this arrangement into the production lineshown in FIGURE 1, it is to be pointed out that the inlet water ifurthest downstream relative to the advancing resin. At this point ithas its lowest temperature, by not having absorbed exothermic heat. Thewater travels upstream against the advancing resin and thus carries awayand immediately disposes of the exothermic heat generated by thepolymerization of the resin. The exotherm is thus uniformly swept awayor carried away, for effective control.

Relative to FIGURE 13, it should be noted that the transverse ribmembers 88 are apertured at 137 at opposite ends, in adjacentunits, toprovide a zigzag flow as schematically illustrated by the arrows 138.This assures uniform distribution of the heat-exchange medium, providinguniform temperature over the entire area of the system.

Level control for the unit is shown in FIGURES 13 and 14. This comprisesa retaining wall 140 of appropriate height to establish a water level142, FIGURE 11, for proper droplet generation. The overflow conduit 136extends through walls 74, 78, and 82 to convey system water back to thetemperature adjusting mechanism, such as a heat exchanger. The reasonwhy this water is not merely spilled into the overflow trough 76 andconveyed away by means of the drain conduits 130 thereof is that thiswater is of a little higher temperature than the loss of spray andleakage that accumulates in the trough 76. Thus, less heat exchange willbe required for this the main flow, and the system can be stabilizedmore effectively than would otherwise be the case.

Rotation of the splasher units 86 Refer to FIGURES 8 and 9 for thisdiscussion. In accordance with the present invention, an individualmotor unit 146 is provided for each pair of adjacent splashers 86. Thus,if one drive unit should go out by malfunction, the remainder willcontinue to operate and production can continue. This is brought aboutby the overlapping center feature and uniform droplet patterndistribution previously discussed. As shown in the upper left corner ofFIGURE 5, each of the shafts 108 is provided with a pulley 148. Theseare also shown in FIG- URES 8 and 9. A motor mount, comprising avertical plate 150, is fastened to the outside wall 82 of overflowtrough 76 between adjacent shafts 108. A horizontal plate 152 projectsoutwardly as shown in FIGURE 8, and in FIGURE 5 in fragment. Thishorizontal plate 152 is of L-shaped configuration and notched to extendover the left hand pulley 148 as shown in FIGURE 9. The motor 154, asshown in FIGURES 8 and 9, sits on the left hand end of plate 152 withthe pulley 156 carried by the shaft thereof, extended out in ali nmentover the left hand pulley 148 of a splasher unit 86.

As shown in FIGURE 9, a belt 158 laps pulley 156 and the two pulleys 148to drive a pair of the splasher units 86.

A indicated in FIGURE 8, elongated slots 160 are formed in plate 152 sothat the motor 154 can be adjusted to tighten the belt 158 as desired.By this arrangement, no extra jack shaft or idler pulley is necessaryfor tightening the belt. To further prevent slippage, toothed belts andpulleys of the timing variety can be used.

The upward spray pattern can be regulated by varying the speed of thesplashers 86, by varying the water level, and by alternating thedirection of rotation of adjacent pairs of splashers, and by orientationof the blades to the direction of rotation so as to scoop the watereffectively,

as previously described and shown by FIGURES 4 and 12.

Brief rszmzc' Looking back for a moment, observe that a system has beenprovided for developing an upwardly projected multiplicity of waterdroplets. These are directed against a mold plate surface opposite whicha polymerizing resin mass is retained for purposes of controlling theexothermic heat developed thereby. This system may be summarized interms of the following characteristics:

Highly uniform droplet distribution over a substantial surface area;

Absence of clogging because of absence of water jets that would besubject to stoppage by deposition of foreign matter and water-carriedchemicals; and

Intimate contact between the heat-exchange medium produced in dropletform and the mold plate for perfect control of the exotherm ofpolymerization of the resin.

The foregoing listing of the characteristics inherent in the presentinvention leads to the conclusion that the general scope of invention isextensible beyond the particular environment shown in FIGURE 1 of thedrawings. Thus, within the brood scope of this disclosure, it iscontemplated that the invention is applicable to the control of apolymerizing resin mass carried on any sheet-like mold surface. Thus,such resin mass may be carried by an individual mold and manipulated byone of the following processes:

(a) Continuous movement along a production line analogous to theproduction line used in describing the environment for the invention;

(b) Incremental movement of such individual mold along a productionline; and

(c) No movement, where the layup, gel-heating of the resin, and then thefinal polymerization with exotherm control are provided by theinvention, all effected at a single station, and on a stationary mold.

Brief descriptions of these extensions of invention are now set out asfollows:

The continuous mold movement process This is shown in FIGURE 15 of thedrawings. An endless wire mesh belt 162 is run over four spaced rolls164 having their axes in alignment. At least one of the rolls 164 ispowered to move belt 162 in the arrow direction 166. On the upper flight168 are placed inverted box-like mold shapes 170. Molds 170 are suitablyformed of thin-walled metal such as cast aluminum or other appropriatematerial to provide good heat-transfer. The upper surfaces of the moldsare appropriately polished and configured to produce a molded image in aresin layup placed thereon. Of course, appropriate release agents willbe used so that the parts can be separated, in accordance with suchskills available to the molder.

Molds 170 are successively placed on the top flight 168 in invertedposition. Inasmuch as droplets of water are thrown upwardly from thecontrol station 172, the molds are suitably flanged as at 171, with theflanges configured to provide an overlap. This prevents the dropletsfrom being thrown up into contact with the accruing resin, and equipmentused on the topside of the upper flight 168. At the left side of upperflight 168 the resin layup is effected at station I. There, choppedstrand and resin are suitably applied by guns designated by thereference numerals 174 and 176. These are combined to provide a layup178 on the molds 170, which are moved in the arrow direction 166 at aconstant speed along with belt 162.

At station 11, a heat source such as a plurality of infrared lamps 180comes into play as the molds 170 pass therebeneath, to initiatepolymerization of the resin in the layup 178.

The gelled layup then progresses in a continuous manner to station IIIwhere the polymerization is completed. The body of water 142 at station172 is maintained at a temperature level such that it acts in a twofoldmanner:

(1) To supply heat to the polymerizing resin, of a sufficient intensityto kick the polymerization reaction up to its final stage of intensity;and

(2) To serve as a heat sink or heat absorber to prevent the resinpolymerization exceeding maximum exotherm level, and thus preventingmonomer boil.

As mentioned relative to FIGURE 13 of the drawings, the flow of theheat-exchange material is kept moving in an upstream direction to theresin so that the exothermic heat is effectively removed within arelatively narrow control zone that becomes critical during theprogressive polymerization of the resin.

By referring to the right side of FIGURE 15, 1t Will be noted that themolds are removed and recycled in the arrow direction 182 after havingbeen passed through a final cure oven, embracing the chain 162, or at aseparate location. This permits the parts to be removed from the molds,and the molds cleaned, treated with release agent, and then recycled tothe head end of the production line designated by the station I. Thechain is recycled on the lower rolls 164 in arrow direction 166.

This process is summarized as a continuous operation wherein a curingresin is exposed to intimate heat exchange contact with a heat exchangemedium whereby the exotherm of reaction is dissipated. In this processthe parts are constantly moving and meet a counter-current temperaturegradient in the form of the countercurrently flowing heat exchangemedium.

The increment process This is shown in FIGURE 16 and utilizes a pair ofrails 184 upon which wheeled molds 186 are traveled. Propulsion may beprovided by a central chain 188 having studs 191 to engage plates 190 ofthe molds 186.

Sprockets 192 support the chain 188 and suitable driving means, such asa motor, drives at least one of the sprockets to propel the chain in thearrow direction 194.

It will be noted that the molds 186 are spaced from one another alongthe rails 184. Thus open gaps between are provided. This requires thatthe control station 172 be operated intermittently, and thus only whilea mold is placed thereover; this prevents the spray from contactingequipment above and around the manufacturing line.

Here, as in the continuous system of FIGURE 15, layup is effected byguns 174 and 176 at station I to produce a layup 178. The chain 188 isthen actuated to move the mold from station I- to station II, whereinthe radiant heat source 180 is activated for a given period of time toinitiate the polymerization of the resin.

Thereafter, chain 188 is indexed forwardly to carry the gelling layupfrom station II to final polymerization sta tion III. Here the mold 186with the polymerization layup 178 thereon is placed in coveringrelationship to the control station 172 to confine the water dropletcomplex there developed. This controls the resin polymerization in amanner analogous to but not exactly like that of the system of FIGURE15. There the resin is constantly moving over the water droplet system,and meeting a countercurrent flow of heat-exchange medium of decreasingtemperature gradient.

In the system of FIGURE 16, the resinous mass remains stationary and theexotherm is removed therefrom by the flow from right to left through thecontrol station 172. There is an approximate duplication of the controlshown in FIGURE 15, but the subtle difference becomes at once apparent.

Upon completion of the polymerization, the station 172 is shut down andthe mold moved therefrom to a postcuring station. The part is thenstripped and the mold recycled to the head end of the production line;with appropriate intermediate maintenance as necessary.

It will be observed that FIGURE 16 represents a slight retrogressionfrom the completely automated and continuously moving system shown inFIGURE 15. The system of FIGURE 16 is thus adapted for use by thesmaller manufacturer whose volume is not so high and who may be layingup more complex articles that are not adapted to the fast layup as wouldbe required by the continuously moving or high speed production lineshown in FIG- URE 15.

The stationary system For the manufacture of extremely large and bulkyarticles such as fiber reinforced resin boats and the like, the systemshown in FIGURE 17 is particularly useful.

Here, the thin walled mold 196 is shown in section as used for producinga boat hull. Actually here the section was taken transversely andcentrally of the boat and does not show either the bow or the sternthereof. This thin walled mold is designated 196 and is positioned overa control system 172 of the present invention.

Operation of this embodiment of the invention is as follows:

With the mold 196 in place and the control system 172 shut down, a layupis made by bringing guns 174 and 176 into play over the surface of mold196 to produce a layup 178 thereon. At the conclusion of this operation,which will usually be a hand operation, but can be automated, a heatsource, such as the infra-red lamps 180, will be actuated and playedover the surface to initiate or bring the polymerization to the gelstage. This may be done on a remote section of the mold after thatportion has been covered with the layup, and the layup operation hasprogressed to another portion of the mold.

At this point, the utility of the present invention becomes at onceapparent. With the polymerization activated to the gel stage, after thelayup is completed, the control system 172 is activated. This can beused to supplement the radiant energy from the heat source 180 and bringthe resin up to polymerization level faster than by the heat source 180alone. Be that as it may, the important point is that once thepolymerization exotherm has been brought to the maximum safe level, thepresent system is immediately available to control the exotherm againstrunaway. Where a boat hull is being made, it

will be evident to those skilled in the art that the mass effectprovided by the total amount of resin available may become a dangerousfactor unless adequate control is provided. In accordance with thepresent invention, using adequate throughput of heat-exchange mediumsuch as water, and the intimate contact provided by the system whereinthe droplets are placed in direct touch with the mold, there is nodanger that resin monomer boil will be produced. There is nodanger thata large article will be rejected because of defects by monomer boil.

It is to be noted that this last embodiment illustrates a still furtherretrogression from a continuous production system back through anincremental system to a stationary system. Thus, the present embodimentillustrates the full range of versatility of the invention.

It is believed that the immediate preceding portion of the descriptionclearly illustrates the extended utility of the invention beyond theproduction of mere fiat panels.

Thus, more complicated shapes can be made, as long as t the underneathside of the mold surface is exposed for direct heat exchange, with theheat-exchange medium being placed thereon in droplet form. Maximum heattransfer is provided.

It should become evident that a further advantag is inherent from theinvention. As shown in the drawings, there is no pressure restriction onthe heat-exchange medium. Thus, it can be vaporized and dispersed to theatmosphere if desired. It is well known that the latent heat ofvaporization of water provides a high heat sink factor; this isavailable if the critically of the resin polymerization exothermrequires it.

As mentioned above, acrylic systems can readily reach a 300 F.temperature level, if the resin runs away. As is evident, this willreadily vaporize water. Automatically this will utilize the latent heatof vaporization of the water. A tremendous control factor is therebybrought into play. This is over and above the heat-exchange that isavailable between the actual temperature of the water beforevaporization, and the polymerizing resin.

Therefore, it is to be understood that the present invention providesuse of latent heat of vaporization as a heat sink in addition tointimate heat-exchange relationship between a body of a heat-exchangeliquid and the polymerizing resin mass.

We claim:

1. In apparatus for curing synthetic resins that produce exothermic heatof reaction during polymerization,

an open top container for a body of liquid heat-exchange material,

a mold plate extended over said container above said body ofheat-exchanger material,

and means for developing a multiplicity of droplets from said body ofheat-exchange material and propelling said droplets into direct contactwith said mold plate.

2. In a system for curing synthetic resins productive of exothermic heatof polymerization,

container means for a body of liquid heat-exchange medium,

a body of liquid heat-exchange medium in said container means,

a mold plate positioned in exposed relation to said heat-exchangeliquid,

and means for splashing liquid from said body of heatexehange materialas a uniform pattern of distinct droplets and propelling said dropletsinto direct heat exchange contact with said mold plate to intimately wetsaid mold plate and thereby provide uniform heat transfer with theresin.

3. In apparatus for forming synthetic resin system exhibiting exotherrnsof polymerization,

an open topped container,

a body of liquid heat-exchange medium in said container,

a thin-walled mold extending at least partially in covering relationshipover said body of liquid with the underside exposed directly to saidliquid,

said mold being formed of a material having high heat conductivity,

means for applying a polymerizable resin system to said mold on thesurface isolated from said body of liquid,

an elongated panel member including an elongated support,

said panel member including an elongated rectangular plate-like surfaceand adjacent said surface a canted late-like flange surface,

said surfaces providing a pocket-like depression therebetween,

and means supporting said panel member and depression for rotation aboutan axis comprising said elongated support member, to dip successfullyinto said body of liquid and pick up increments of liquid therefrom andthrow said increments as droplets onto said exposed underside of saidthin-walled mold.

4. In apparatus for curing synthetic resins productive of exothermicheat of reaction during polymerization,

an open-top container,

a body of liquid heat-exchange medium in said container,

a mold plate extending over said body of liquid, with the undersideexposed directly to said liquid,

said mold plate being formed of heat-conductive material,

means for applying polymerizable resin to said mold plate opposite theside exposed to said body of heatexchange material,

and means in said container for developing a multiplicity of dropletsfrom said body of heat-exchange material and propelling said dropletsinto direct contact with said mold plate.

5. In a heat-exchange system,

an open-top tank,

a splasher positioned horizontally within said tank and comprising,

an elongated shaft,

at least one elongated paddle member supported axially along said shaft,

said paddle member including a first elongated rectangular plate-likeblade extending axially along and in contact with said shaft,

a second elongated rectangular plate-like blade extending axially alongsaid shaft and edge-joined to said first blade,

said blades being canted relative to one another to form a pocket-likedepression therebetween,

means for maintaining a body of liquid heat-exchange medium in saidtank,

and means for rotating said splasher member about its axis whereby saidsplasher dips into said body of liquid and picks up increments therefromand throws said increments as droplets out of said tank.

6. In a system for molding polymerizable resins,

a movable, porous conveyor,

means for moving said conveyor continuously in a lineal direction,

a mold positioned on said conveyor and movable therewith,

means for developing a wet resin layup on said mold and isolated fromsaid 'conveyor,

means for initiating polymerization of said resin,

an open-top container beneath a part of said conveyor,

a body of liquid heat-exchange medium in said container,

and rotatable means within said container to develop a plurality ofdroplets from said heat-exchange liquid and propel the droplets throughsaid conveyor and into heat-exchange relationship to the bottom side 13of said mold as said mold is moved thereover by said conveyor. 7. In asystem for molding polymerizable resins exhibiting exotherm of reaction,

a mold,

means supporting said mold for movement in a linear manner,

means for movin said mold stepwise between spaced stations positionedabove said mold and along its path of travel,

means at one of said stations for developing a wet resinlayup on saidmold,

means at another of said stations for initiating polymerization of theresin,

and another of said stations comprising a polymerization control stationand including,

an open-top container supported so that said mold can be movedthere-across,

a body of liquid heat-exchange medium in said container,

and means within said container to develop a plurality of droplets fromsaid heat-exchange liquid and propel the droplets out of said containerand against said mold but Without contacting said layup, to be inheat-exchange contact with said resin through said mold.

a shell-like, thin-walled mold,

means supporting said mold at a fixed position in space,

means for developing a wet resin layup on one side of said mold,

means for initiating polymerization of said resin,

an open-top container beneath said mold,

a body of liquid heat-exchange medium in said container,

and means Within said container to develop a plurality of droplets fromsaid heat-exchange liquid and propel the droplets out of said containerand against the opposite surface of said mold and into intimateheat-exchange relationship to the resin carried thereon.

References Cited UNITED STATES PATENTS 1,311,613 7/1919 Mungry.1,390,005 9/ 1921 Young. 3,233,287 2/ 1966 Blue et al. 3,242,528 3/ 1966Elder.

25 WILLIAM J. STEPHENSON, Primary Examiner.

